A transmission provides different gear ratios between the engine and drive wheels of a typical land vehicle. The transmission enables the vehicle to accelerate from rest up to a maximum speed through a wide speed range while the engine operates efficiently. In most applications, the transmission is positioned in the vehicle power train between the engine and the propeller shaft. The engine's power flows through the transmission and propeller shaft and is delivered to the differential and drive axles.
Most vehicle transmissions operate within a preset range of gear ratios. This is a problem for special purpose vehicles, such as pickup trucks, used for carrying or towing heavy loads. Excessive engine and transmission wear, fuel consumption, and operating costs can result from gear ratios that are set too low at the time of their manufacture, "gear ratio" being defined as output speed divided by input speed. A need, therefore, exists for an "add-on" assembly which can be easily and economically inserted into the power train of a vehicle for increasing the gear ratio between the engine and drive axles. Moreover, there is need in passenger cars, boats, ships, helicopters, small trucks, heavy trucks, front wheel drives and motorcycles for improved efficiency and reduction in air pollution which results from improved efficiency.